Sore from exertion (4)
I believe the answer is:
achy
'sore from exertion' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for achy that I've seen before include "Dully painful" , "suffering dull pain" , "Giving pain" , "Causing steady dull pain" , "Feeling in need of an aspirin?" .)